Wireless devices generate electromagnetic (EM) signals, typically within the electromagnetic spectrum at a Radio Frequency (RF) capable of propagating to other wireless devices for communication purposes. When an electromagnetic signal generated by a source is provided to a load, such as to an antenna, a portion of the signal can be reflected back from the load. An electromagnetic coupler can be included in a signal path between the source and the load to provide an indication of forward power of the electromagnetic signal traveling from the source to the load and/or an indication of reverse power reflected back from the load. Electromagnetic couplers include, for example, directional couplers, bi-directional couplers, multi-band couplers (e.g., dual band couplers), and the like.
An EM coupler typically has an input port, an output port, a coupled port, and an isolated port. When a termination impedance is presented to the isolated port, an indication of forward EM power traveling from the input port to the output port is provided at the coupled port. When a termination impedance is presented to the coupled port, an indication of reverse EM power traveling from the output port to the input port is provided at the isolated port. The termination impedance is typically implemented as a 50 Ohm shunt resistor in a variety of conventional EM couplers.
An EM coupler has a coupling factor, which represents how much power is provided to the coupled port of the EM coupler relative to the power of an EM signal at the input port. EM couplers typically cause an insertion loss in an EM signal path. Thus, an EM signal received at the input port of an EM coupler generally has a lower power when provided at the output port of the EM coupler. Insertion loss can be due to a portion of the EM signal being provided to the coupled port (or to the isolated port) and/or to losses associated with the main transmission line of the EM coupler. In addition, traditional EM couplers add insertion loss to a signal path even when unused. This can degrade an EM signal even when the EM coupler is not being used to detect power.